1. Field of the Invention
This invention relates to coupling devices and in particular fluid line coupling devices which are suitable for connecting pneumatic line segments, hydraulic line segments, fuel line segments or other fluid line segments, tubes, ducts, conduits and the like. More specifically, this invention relates to self-locking coupling devices which are designed to prevent inadvertent disassembly and as a result are capable of operating in severe vibrational and thermal cycling environments while maintaining a leak-free fluid connection.
2. Description of the Prior Art
A variety of coupling devices are known in the art for connecting high pressure fluid line segments and the like. Many of these devices have been specifically designed to prevent inadvertent disassembly and catastrophic leakage during operation. These devices include conventional lockwire fluid fittings which consist of threaded fittings coupled together by wired fasteners which prevent the fittings from rotating apart during operation. However, conventional lockwire fluid fittings are labor intensive to install and as a result are not a preferred coupling system where multiple couplings are required in a single installation.
Other prior art devices include for example, U.S. Pat. No. 5,083,819 to Bynum which discloses a threaded fluid coupling equipped with a fastener capture device. The coupling device comprises an internally threaded female fitting formed with external flats about its circumference and an externally threaded male fitting configured with a plurality of tangs mounted above the external threads in a circumferential fashion. Upon engagement of the male and female fittings, the tangs contact the flats with an interference fit and rachet about the junctions between the flats until the fittings are securely coupled. Once coupled, the tangs and the flats cooperate to inhibit rotation of female fitting relative to the male fitting to prevent an inadvertent disassembly of the coupling.
U.S. Pat. No. 5,058,930 to Schlosser discloses a high pressure coupling device consisting of a coupling component with internal threads which engage the external threads of a nipple. The coupling component includes a cylindrical arrangement of cantilevered fingers with bulbous tips at their ends projecting radially inward which, upon engagement of the respective internal and external threads, ride up a frusto-conical ramping surface on the nipple until the tips drop into an annular groove in the nipple wall. Cantilevered forces in the fingers created as the bulbous tips press against the ramping surface act to provide tight engagement of the threads and serve to minimize the effects of vibration thereupon. The bulbous tips seated in the annular groove are intended to prevent a complete disconnecting of the coupling component from the nipple, a separation which would cause a catastrophic leakage at the joint.
Although the above described coupling devices can be used effectively in some applications, these devices lack positive locking features and as a result can be disconnected by simply applying a torsional force to the coupling members sufficient overcome the retaining features which are intended to inhibit relative rotation and prevent disassembly of the coupling.
What is needed and heretofore unavailable is a self-locking coupling device which, once securely coupled, cannot be disconnected regardless of the amount of torsional force applied to the respective coupling members.
A preferred embodiment of the present invention is directed to a self-locking fluid line coupling device for connecting two coaxial conduits together allowing the flow of fluid therethrough. The self-locking coupling device consists of a first fitting, a second fitting and a locking sleeve mounted about the outer periphery of the first fitting. The self-locking coupling device is designed in such a manner that once the fittings are securely connected, to allow the flow of fluid therethrough, they cannot rotate or translate axially relative to one another. Alternate embodiments of the coupling device of the present invention may be used to join conduits, rods or other bodies together.
The first fitting is formed with a hollow cylindrical body having a coupling portion adjacent a first end and a locking portion adjacent a second end. The coupling portion includes an internal thread section formed about the inner wall of the first fitting. The locking portion includes a plurality of locking tangs attached to the coupling portion extending to the second end of the first fitting. The locking tangs are equally spaced about the axis of the fitting in a cylindrical fashion with radially inward projecting bulbs cooperating to form an internal locking shoulder at the second end. The internal locking shoulder is configured with axially opposed ramping surfaces converging at their most radially inward extremes to form a flat portion.
The first end of the first fitting includes an annular groove recessed into the inner wall for receiving a thrust wire. The annular groove and the thrust wire cooperated to provide a retention ring which captures a ferrule. The ferrule is formed with a hollow cylindrical body having a retention flange at one end. The ferrule extends though the first fitting and attaches to a first conduit such that the retention ring formed about the inner wall of the first fitting and projecting radially inwardly captures the retention flange maintains the ferrule within the first fitting. The outer diameter of the ferrule is sized to closely fit within the inner diameter of the thrust wire. This permits the body of the ferrule to slide though the thrust wire where it is retained by the retention flange. Once the thrust wire is seated against the retention flange the first fitting is free to rotate about the ferrule.
The second fitting is formed with a hollow cylindrical body having a first end and a second end. The first end is configured with a frusto-conical tip designed to engage the corresponding countersunk surface of the ferrule disposed within the first fitting. The second fitting is formed with a external thread section adjacent to the first end to engage the corresponding internal thread section of the first fitting. An annular ridge projecting radially outward is disposed between the external thread section and the second end of the second fitting. Engagement of the corresponding internal and external thread sections advances the first and second fitting together causing the locking tangs to bend and flex radially thereby allowing the internal shoulder to ride up and over the annular ridge.
A locking sleeve is mounted about the exterior of the first fitting and is movable from a unlocked position to a locked position. The locking sleeve being in the unlocked position when it is disposed about the coupling portion of the first fitting whereby the first and second fittings can engage one another to form a coupling allowing fluid flow therethrough. When the first and second fittings are securely coupled together and the internal shoulder is captured behind the annular ridge the locking sleeve is moved to the locked position wherein it is positioned about the locking portion of the first fitting such that the locking sleeve, the internal shoulders on the locking tangs and the annular ridge cooperate to prevent relative rotation and axial translation of the first fitting relative to the second fitting.
The device is designed to positively lock two coaxial conduits together and prevent inadvertent disassembly of the coupling barring a catastrophic failure of the components themselves. As a result, the present invention is capable of operating in severe vibrational and thermal cycling environments while maintaining a leak-free fluid connection. The present invention is also capable of reducing installation time and production cost because design features incorporated into the device provide visible and tactile feedback of correct installation.
Other features and advantages of the present invention will become more apparent from the following detailed description of the invention, when taken in conjunction with the accompanying exemplary drawings.